For a long time foodstuffs, whether foodstuffs for human consumption or also animal feed products, have been preserved by being stored either in a can or in a glass jar closed with a lid. However, these packaging systems have some serious disadvantages, inter alia the high intrinsic weight, the energy-intensive production and the troublesome opening.
Alternative packaging systems for storing foodstuffs for a long period of time as far as possible without impairment are known from the prior art. These are containers produced from planar composites—often also called laminate. Such planar composites are often built up from a layer of thermoplastic, a carrier layer usually made of cardboard or paper, an adhesion promoter layer, an aluminium layer and a further layer of plastic. Such a planar composite is disclosed, inter alia, in WO 90/09926. Such laminated containers already have many advantages over the conventional glass jars and cans, for example space-saving storage and low intrinsic weight.
The use of “low-density polyethylene, LDPE” layers in the production of containers such as are described in EP 1 020 480 and EP 1 777 238 represents a further development of such planar composites. In these, the polymer coatings are produced by an autoclave process with a subsequent extruding process of the polymer on a carrier. A controlled pressure and temperature programme for the production process can be achieved with the aid of these autoclave processes. Nevertheless, possibilities for improvement also exist for these packaging systems.
Thus, in the production process, in particular during application of the polymer layers of the abovementioned containers, tearing off of the PE layers or perforation occurs again and again, especially in the creasing regions of the containers. Damage and defects in the packaging can consequently occur, as a result of which this is damaged visually and functionally, above all inside the planar composite. This is particularly undesirable, since this step is at the end of the creation of value and higher costs are therefore caused by withdrawal of damaged packs and claims due to leaks.
In the case of containers with scores in particular, in these chiefly at the container creasing points, such tearing off of the polymer layer can lead to malfunctions, such as leakiness, which are noticed only during use, for example filling or even only later by shortened storage times of such a container.
Generally, the object of present invention is to at least partly eliminate the disadvantages emerging from the prior art.
The object is furthermore to provide a planar composite which has a high stability and leakproofness.
An object is furthermore to provide a container from a composite, wherein the container can be produced by easy folding of the composite and at the same time should have a high leakproofness. The container should therefore be particularly well-suited to long-term storage of sensitive foodstuffs.
A further object is to provide a planar composite which can be produced efficiently and inexpensively.
An object in turn is to provide a planar composite which can be produced as quickly as possible and without a high reject rate.
A further object is to provide a planar composite which is suitable in particular for the production of containers for transportation and storage of foodstuffs, animal feeds, drinks of low carbonic acid content and the like.
An object is furthermore to provide a process for the production of a planar composite which is as far as possible efficient and inexpensive as well as fast and of low susceptibility to defects.
A further object is to improve the processability of the materials used in the production, in particular to minimize the neck-in during application of thermoplastics by extrusion, in particular of PE layers. A further object in turn is to increase the speed in the production of planar composites, in particular to optimize the draw-down ratio of the materials to be processed.
An object is furthermore to provide a planar composite which tends towards as few defects as possible, in particular during folding in the cold, as a result of which a packaging container having a good leakproofness can be produced.